Double knit fabric

ABSTRACT

A double-knit fabric containing a first knit layer, a second knit layer, and a plurality of stuffer yarns. The stuffer yarns are located between the first knit layer and the second knit layer. The double-knit fabric contains a plurality of anchored regions and a plurality of detached regions. In the anchored regions, the first and second fabric layers are knitted together and in the detached regions the first and second fabric layers are unattached. The average peak distance between the first and second fabric layers in the detached regions is at least about 3 mm and the double-knit fabric has between about 10 and 30 detached regions per square inch. The anchored regions contain at least two knit stitches in at least one direction and the anchored regions have a width of at least about 1 mm.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed double-knit fabrics, more particularlyto double-knit fabrics for garments.

BACKGROUND

Performance fabrics manufactured for use in insulating garments ofteninclude fleece fabric, i.e. fabric having a raised or brushed fibersurface for improved insulation performance. The surface of such fabricsis often formed of fleece, which is raised, i.e., given relativelyhigher loft, by mechanical brushing. It has, however, been recognizedthat the brushing process can often result in broken fibers, which, overtime, can work loose, potentially resulting in microfiber pollution.Loss of fibers, e.g., during washing, can also result in deteriorationof insulation performance. Further, it is recognized that broken fibersreleased during washing can get into wastewater, causing pollution. Itis desirable to have a low fiber loss, low weight, and high insulativefabric for use in outerwear and other garment uses.

BRIEF SUMMARY OF THE INVENTION

The invention relates to a double-knit fabric having an upper surfaceand a lower surface and having a warp and weft direction, where the weftdirection is perpendicular to the warp direction. The double-knit fabriccontains a first knit layer comprising a plurality of first yarns, asecond knit layer comprising a plurality of second yarns, and aplurality of stuffer yarns. The first knit layer forms the upper surfaceof the double-knit fabric and the second knit layer forms the lowersurface of the double-knit fabric. The stuffer yarns are located betweenthe first knit layer and the second knit layer.

The double-knit fabric contains a plurality of anchored regions and aplurality of detached regions, where the plurality of detached regionsis interspersed between the anchored regions. In the anchored regions,the first fabric layer and the second fabric layer are knitted togetherand in the detached regions the first fabric layer and second fabriclayer are unattached.

The first knit layer and the second knit layer are integrated within theanchored regions at least one method selected from the group consistingof interlacing first yarns of the first knit layer among the secondyarns of the second knit layer, interlacing the second yarns of thesecond knit layer among the first yarns of the first knit layer, andinterlacing a plurality of third yarns among the first yarns of thefirst knit layer and the second yarns of the second knit layer.

The average peak distance between the first fabric layer and the secondfabric layer in the detached regions is at least about 3 mm and thedouble-knit fabric has between about 10 and 30 detached regions persquare inch. The anchored regions contain at least two knit stitches inboth the warp and weft directions and the anchored regions have a widthof at least about 1 mm in both the warp and weft directions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a cross-section of the double-knit fabricaccording to one embodiment of the invention.

FIG. 2 a is photograph of the upper surface of the double-knit fabricaccording to one embodiment of the invention. FIG. 2 b is illustrationof the photograph of FIG. 2 a.

FIG. 3 a is angled photograph of the double-knit fabric according to oneembodiment of the invention. FIG. 3 b is illustration of the photographof FIG. 3 a.

DETAILED DESCRIPTION

Referring now to FIG. 1 , the double-knit fabric 10 of the invention hasan upper surface 10 a and a lower surface 10 b, a warp direction and aweft direction (where the weft direction is perpendicular to the warpdirection), and contains a first knit layer 20, a second knit layer 30,and a plurality of stuffer yarns 40. The first knit layer 20 forms theupper surface 10 a of the double-knit fabric 10, the second knit layer30 forms the lower surface 10 b of the double-knit fabric 10, and thestuffer yarns 40 are located between the first 20 and the second 30 knitlayers.

The detached regions 420 are interspersed between the anchored regions410. In the anchored regions 410, the first fabric layer 20 and thesecond fabric layer 30 are knitted together (forming a single unitaryknit layer) and in the detached regions 420 the first fabric layer 20and second fabric layer 30 are unattached (and are separate knitlayers). This knitting of the first knit layer and the second knit layeris done at the same time on the same knitting machine as knitting thefirst knit layer and the second knit layer. This is contrasted to aquilted fabric where the two layers are formed separately and thenstitched together. The stuffer yarns 40 are bulky yarns (shown goinginto the plane of the illustration) fill out the detached region 420 andgive them their bump appearance. The detached regions may have anysuitable shape, including, but not limited to squares, rectangles,ovals, octagons, hexagons, irregular amoeba-like shapes, jellybeans,diamonds, and elongated lines. Preferably, the detached regions are in aregular grid (which does include a horizontal/vertical grid, offsetgird, brick pattern grid, and more).

The detached regions 420 and attached regions 410 may form varyingamounts of the surface area of the upper surface 10 a of the double-knitfabric 10 depending on the end use. Because the detached regions 420tend to be more insulating, it is preferable to increase the amount ofsurface area of the detached regions 420 relative to the surface area ofthe upper surface 10 a of the double-knit fabric 10. In one preferredembodiment, the detached region 420 form between about 60 and 99% of thesurface area of the upper surface of the double-knit fabric, morepreferably between about 75 and 98%, more preferably between about 85and 96%.

In FIG. 2 a , there is shown a photograph of the upper surface 10 a ofthe double-knit fabric 10 which shows the surface of the first knitlayer 20. In this picture, one can see the “bumps” on the fabric whichare the detached regions 420 and the lines that bound the grid of bumpsbeing the attached regions 410. FIG. 2 b is an illustration of FIG. 2A.In FIG. 3 a , there is shown a photograph of the cross-section of thedouble-knit fabric 10 so one can more easily see the detached regions420 and the attached regions 410. FIG. 3 b is an illustration of FIG.3A.

Preferably, the double-knit fabric has between about 10 and 30 detachedregions per square inch, more preferably between about 15 and 25detached regions per square inch. It has been found that this range ofregions per square inch produces an insulative fabric that has goodweight, thickness, and aesthetics. In one embodiment, the detachedregions 420 preferably have at least one dimension in the plane of thedouble-knit fabric 10 of at least about 1 mm, more preferably at leastabout 2 mm, more preferably at least about 3 mm. Each of the detachedregions 420 contain a plurality of knit stitches.

Each of the anchored regions 410 contain at least two knit stitches inat least one of the warp and weft directions which is a departure fromother double-knitted fabrics. In a preferred embodiment, the anchoredregions 410 contain at least two knit stitches in both the warp and weftdirections. In another embodiment, each of the anchored regions 410contain at least three knit stitches in at least one of the warp andweft directions, more preferably in both directions. In anotherembodiment, the anchored regions 410 have a width of at least about 1 mmin both the warp and weft directions, more preferably at least about 1.8mm in both the warp and weft directions.

How tall or high the detached regions 420 are also contributes to theinsulative value and look to the fabric. In one embodiment, the averagepeak distance between the first fabric layer and the second fabric layerin the detached regions is at least about 3 mm. The average peakdistance is calculated by measuring the distance between the innersurfaces (the surfaces facing each other) of the first knit layer andthe second knit layer. This distance is measured on at least 10different detached regions and then the result is averaged. In anotherembodiment, the average peak distance between the first fabric layer andthe second fabric layer in the detached regions is at least about 3.5mm, more preferably at least about 4.0 mm.

In addition to the average peak distance, the entrained air factor canalso be an important characteristic of the fabric. This entrained air isthe air located between the upper surface 10 a of the double knit fabric10 and a wearer's skin. This additional air also serves to insulate thewearer. The following procedure was used to calculate a measure of theentrained air.

A Keyence VHX-6000 was used to obtain a three-dimensional image of thedouble-knit fabric. The image should represent an area at least 2.9cm×3.5 cm on the double-knit fabric surface. The topography (alignedwith the dominant symmetry directions of the material) of the uppersurface 10 a of the double-knit fabric 10 was generated using theprofile line tool available with the Keyence VHX-6000. The profilegenerated was an average profile, where the range is set at 5 lines andthe interval is set on 300 μm. This amounts to averaging the profiles of11 lines (5 on either side of the center line), all separated by 300 mm,or 0.03 cm. This has the effect of averaging out the fluctuations inheight due to individual yarn variations. The center line for thisprofile is oriented along the targeted direction and centered on thehigh points/center of the detached regions in the profile direction. Foreach image of a fabric specimen, there are often multiple rows andcolumns (at approx. Right angles to each other) of the repeatedstructure of detached regions. A profile is formed as described abovefor each distinct row and column.

The targeted metric of analysis is related to the air space that wouldbe formed if the fabric was laid against a surface and the high pointsof the profile touched the surface. The air space above the top surfaceof the fabric and an imaginary line that connects to the high points ofthe profile for each repeat unit is calculated. To do this, the profileis delineated into segments that reflect the repeat units along thedirection the profile represents. The high point of the profile for eachone of these segments is determined using mathematical tools (such asExcel). Within a spreadsheet, a straight line, representing a boundinglayer if the high points were laying against a surface, is calculatedbetween the high points of neighboring repeat units of the profile. Atthe edges of the profile, one of two things happens. If there is amaximum point at the edge of the profile, the straight line goes to thathigh point. If there is not a high point on the edge, the line extendsfrom the nearest maximal point in the profile to a height which is anaverage height of the maximal points on the profile at the two extremesof the profile. Once this bounding line is calculated, the difference ateach point in the profile between the bounding line and the top of theprofile is calculated. A numeric integral is calculated of the areabetween the top of the profile and the bounding line. This area is thendivided by the length of the image in that profile direction. Thisprovides an entrained air height for that row or column of the image.This entrained air height is then calculated for each distinct row andcolumn of the image and averaged together, providing the averageentrained air height for that specimen. Preferably, the averageentrained air height is between about 0.3 mm and 25 mm. In anotherembodiment, the calculated entrained air is between about 0.4 and 25 mm.In another embodiment, the calculated entrained air is between about 0.5and 25 mm.

The first knit layer 20 contains a plurality of first yarns and thesecond knit layer 30 contains a plurality of second yarns. The yarnsthat make up these layers can be any suitable yarn. “Yarn”, in thisapplication, as used herein includes a monofilament elongated body, amultifilament elongated body, ribbon, strip, yarn, tape, fiber and thelike. The knit layers 20, 30 may contain one type of yarn or a pluralityof any one or combination of the above. The yarns may be of any suitableform such as spun staple yarn, monofilament, or multifilament, singlecomponent, bi-component, or multi-component, and have any suitablecross-section shape such as circular, multi-lobal, square or rectangular(tape), and oval.

The yarns of the knit layers 20, 30 may be formed of (but are notlimited to) cellulosic yarns (such as cotton, rayon, linen, jute, hemp,cellulose acetate, and combinations, mixtures, or blends thereof),polyester yarns (e.g., poly(ethylene terephthalate) yarns,poly(propylene terephthalate) (PET) yarns, poly (trimethyleneterephthalate) yarns), poly(butylene terephthalate) yarns, and blendsthereof), polyamide yarns (e.g., nylon 6 yarns, nylon 6,6 yarns, nylon4,6 yarns, and nylon 12 yarns), polyvinyl alcohol yarns, an elasticpolyester-polyurethane copolymer (SPANDEX®), polypropylene yarns,polyethylene yards, polyvinyl acetate yarns, polylactic acid yarns,flame-resistant meta-aramid (NOMEX®) or para-aramid, and combinations,mixtures, or blends thereof. In one preferred embodiment, the knitlayers 20, 30 contain multifilament polyester yarns as these have beenshown to have good performance at low cost. In one embodiment, the firstand second knit layers 20, 30 contain essentially all (defined as beingat least about 98% by weight) multifilament polyester yarns. In oneembodiment, the yarns that make up the knit layers 20, 30 all haveapproximately the same thickness or denier. In other embodiments, thereis a difference in denier. In another embodiment, there may be more thanone type of yarn within a knit layer (varying in materials,construction, and/or denier) or the yarns used may contain more than onetype of fiber. In one embodiment, at least one of the first and secondknit layers 20, 30 contains either nylon fibers or yarns.

Referring back to FIG. 1 , there are also fabric also contains aplurality of stuffer yarns 40 located between the first knit layer 20and the second knit layer 30. These stuffer yarns may be any suitableyarn and are preferably bulky so that they fill up the areas between thefirst and second knit layers and provides insulation. Preferably, thestuffer yarns are a multifilament polyester yarn. It has been shown thatpolyester yarns may be easily bulked and retain their volume over time.In one preferred embodiment, the stuffer yarns are faux twist texturedyarns. Preferably, the stuffer yarns run approximately parallel to eachother in the weft direction of the double-knit fabric.

In one preferred embodiment, the entire fabric is mostly polyesteryarns, more preferably continuous multifilament polyester yarns. Inanother embodiment, the entire fabric (including the first knit layer,the second knit layer, the stuffer yarns, and any additional yarns) isessentially all (defined as at least 98% by weight) polyester yarns,more preferably continuous multifilament polyester yarns.

Thickness of both layers 20, 30 may be any suitable thickness and may beapproximately equally distributed, or one of the layers may thicker thanthe other. Typical thickness of the fabric is between about 0.1 and 6mm, more preferably between about 1 and 4 mm.

The two knit layers 20 and 30 may be combined, knitted, and joinedtogether (during knitting) in any suitable manner. A first method isinterlacing first yarns from the first knit layer 20 among the secondyarns of the second knit layer 30, meaning that a portion of the yarnsfrom the first knit layer leave the first knit layer, travel down intothe second knit layer where they are interlaced with yarns within thesecond knit layer, and then travel back up to the first knit layer.

A second method is interlacing second yarns from the second knit layer30 among the yarns of the first knit layer 20, meaning that a portion ofthe yarns from the second knit layer 30 leave the second knit layer,travel up into the first knit layer where they are interlaced with yarnswithin the first knit layer, and then travel back down to the secondknit layer to the first knit layer.

A third method is interlacing a plurality of additional yarns in amongthe yarns of the first knit layer 20 and the yarns of the second knitlayer 30. This means that an additional yarn (which may be the same ordifferent yarn than the yarns in the first or second knit layers)travels between the layers, interlacing with yarns from both layers andin essence, tying them together. This additional yarn may be selectedfrom any of the yarns described in reference to the yarns in the firstknit layer.

In a preferred embodiment, the second method is used to interlace andknit the first 20 and second 30 knit layers together. This method may bepreferred because of the lower complexity during the knitting processusing the circular knitting.

Preferably, the double-knit fabric has a clo value measured by test ASTMF1868 of at least about 0.2. Clo is a measure of insulative value of thefabric. In another embodiment, the double-knit fabric has a clo valuemeasured by test ASTM F1868 of at least about 0.3, more preferably atleast about 0.4. In another embodiment, 9. The double-knit fabric ofclaim 1, wherein the double-knit fabric has an air permeability of atleast about 150 CFM, more preferably about 175 CFM, more preferablyabout 200 CFM, and more preferably about 225 CFM.

When the fabric 10 is made into an article of clothing (also referred toas a garment), in one embodiment the lower surface 10 b would be facingaway from the wearer and upper surface 10 a would be facing towards thewearer. In another embodiment, the lower surface 10 b would be facingthe wearer and upper surface 10 a would be facing away from the wearer.The double-knit fabric 10 is a unitary material that is formed togetherin a knitting machine with the two layers sometimes being separate andsometimes knitted together. The layers 20 and 30 are not formed asdiscrete knit layers and then joined together in a later operation. Thefabric 10 may be made by any suitable knitting method, including bothwarp knitting and weft (or circular) knitting. Circular knitting ispreferred in some embodiments, as it tends to be more cost efficient.The article of clothing may be any suitable article including but notlimited to a shirt, jacket, pants, tights, leggings, hat, undergarments,and socks.

In another embodiment, a garment may use the fabric in addition to otherfabric. For example, a shirt might use the fabric of the invention onthe torso and another fabric in the sleeves. Additionally, the fabric ofthe invention could also be used as an insert. Additionally, the fabricmay be used for any other suitable purpose including, but not limitedto, a tent, automobile covering, upholstery, mattress covers, and petbeds.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the subject matter of this application (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The terms “comprising,” “having,”“including,” and “containing” are to be construed as open-ended terms(i.e., meaning “including, but not limited to,”) unless otherwise noted.Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the subject matter of theapplication and does not pose a limitation on the scope of the subjectmatter unless otherwise claimed. No language in the specification shouldbe construed as indicating any non-claimed element as essential to thepractice of the subject matter described herein.

Preferred embodiments of the subject matter of this application aredescribed herein, including the best mode known to the inventors forcarrying out the claimed subject matter. Variations of those preferredembodiments may become apparent to those of ordinary skill in the artupon reading the foregoing description. The inventors expect skilledartisans to employ such variations as appropriate, and the inventorsintend for the subject matter described herein to be practiced otherwisethan as specifically described herein. Accordingly, this disclosureincludes all modifications and equivalents of the subject matter recitedin the claims appended hereto as permitted by applicable law. Moreover,any combination of the above-described elements in all possiblevariations thereof is encompassed by the present disclosure unlessotherwise indicated herein or otherwise clearly contradicted by context.

What is claimed is:
 1. A double-knit fabric having an upper surface anda lower surface and having a warp and weft direction, wherein the weftdirection is perpendicular to the warp direction, wherein thedouble-knit fabric comprises: a first knit layer comprising a pluralityof first yarns, wherein the first knit layer forms the upper surface ofthe double-knit fabric; a second knit layer comprising a plurality ofsecond yarns, wherein the second knit layer forms the lower surface ofthe double-knit fabric; and, a plurality of stuffer yarns, wherein thestuffer yarns are located between the first knit layer and the secondknit layer; wherein the double-knit fabric comprises a plurality ofanchored regions and a plurality of detached regions, wherein theplurality of detached regions are interspersed between the anchoredregions, wherein in the anchored regions the first yarns from the firstfabric layer and the second yarns from the second fabric layer areknitted together, and wherein in the detached regions the first fabriclayer and second fabric layer are unattached; wherein the first knitlayer and the second knit layer are integrated within the anchoredregions at least one method selected from the group consisting ofinterlacing first yarns of the first knit layer among the second yarnsof the second knit layer, interlacing the second yarns of the secondlayer among the first yarns of the first knit layer, and interlacing aplurality of third yarns among the first yarns of the first knit layerand the second yarns of the second knit layer; wherein the average peakdistance between the first fabric layer and the second fabric layer inthe detached regions is at least about 3 mm, wherein the double-knitfabric has between about 10 and 30 detached regions per square inch,wherein the anchored regions comprise at least two knit stitches in atleast one of the warp and weft directions, wherein the anchored regionshave a width of at least about 1 mm in both the warp and weftdirections.
 2. The double-knit fabric of claim 1, wherein the averagepeak distance between the first fabric layer and the second fabric layerin the detached regions is at least about 3.5 mm.
 3. The double-knitfabric of claim 1, wherein the double-knit fabric has between about 15and 25 detached regions per square inch.
 4. The double-knit fabric ofclaim 1, wherein the anchored regions comprise at least three knitstitches in at least one of the warp and weft directions.
 5. Thedouble-knit fabric of claim 1, wherein the anchored regions have a widthof at least about 1.8 mm in both the warp and weft directions.
 6. Thedouble-knit fabric of claim 1, wherein the double-knit fabric has a clovalue measured by test ASTM F1868 is at least about 0.2.
 7. Thedouble-knit fabric of claim 1, wherein the double-knit fabric has a clovalue measured by test ASTM F1868 is at least about 0.3.
 8. Thedouble-knit fabric of claim 1, wherein the double-knit fabric has a clovalue measured by test ASTM F1868 is at least about 0.4.
 9. Thedouble-knit fabric of claim 1, wherein the double-knit fabric has an airpermeability of at least about 150 CFM.
 10. The double-knit fabric ofclaim 1, wherein the double-knit fabric has an air permeability of atleast about 200 CFM.
 11. The double-knit fabric of claim 1, wherein thedetached areas have at least one dimension within the plane of thedouble-knit knit of at least about 3 mm.
 12. The double-knit fabric ofclaim 1, wherein the stuffer yarns run generally parallel to each other.13. The double-knit fabric of claim 1, wherein the first layer and thesecond layer are integrated through combined portions formed byinterlacing first yarns of the first knit layer among the second yarnsof the second knit layer.
 14. The double-knit fabric of claim 1, whereinthe first yarns are polyester yarns.
 15. The double-knit fabric of claim1, wherein the double-knit fabric consists essentially of polyester,defined as being at least 98% by weight polyester.
 16. The double-knitfabric of claim 1, wherein the detached regions have an irregular ovalshape in a repeating grid pattern.
 17. The double-knit fabric of claim1, wherein the upper surface of the double-knit fabric comprises atopography formed from the anchored and detached regions, wherein thetopography has an average entrained air height of between about 0.3 mmand 25 mm.
 18. A garment comprising the double-knit fabric of claim 1.19. The garment of claim 18, wherein the garment is selected from thegroup consisting of a jacket, pants, hat, and shirts.